The most common scam involves legitimate rental offers, which scam artists are doctoring and posting on listing services such as Craigslist for lower rents, agents say. Eager victims send deposits only to learn that the apartment's actual owner knew nothing of the deal. The deposit, of course, is never seen again.

"We are seeing more and more people looking for rentals," says
Jason Boone,
a research associate at the National White Collar Crime Center, which fields and collates online-fraud complaints for the Federal Bureau of Investigation. "This gives scammers a lot of incentives to be creative and we're seeing an overall increase in the number of rental scams."

Close to 5,500 rental-scam complaints were received nationwide by the start of October, Mr. Boone says. That puts 2010 on track to possibly eclipse last year's record 7,225 complaints.

Statistics for New York alone aren't available. But
Stephen Kotler,
executive vice president and director of rentals at Manhattan real-estate agency Prudential Douglas Elliman, says the firm was aware of three cases in the past two months alone where suspicious would-be renters contacted the firm and established that listings had been copied by bogus operators.

"We have definitely seen an increase in this type of fraud recently," he says. "With the Internet it is very easy for people to scrape information from any website and present it as their own."

Gary Malin,
president of Manhattan real-estate agency CitiHabitats, says renters needed to be particularly vigilant in the current market. "You should never be in a circumstance where you end up reading something that sounds great and people you have never met are asking you to wire money for a place you haven't even seen," Mr Malin says.

His advice: "The smartest thing for anyone to do is to say 'let's get in touch tomorrow' to give you time to examine the situation."

Craigslist spokeswoman Susan MacTavish Best says the site goes to "great lengths" to prevent scams, employing a wide array of measures such as warning users "at every turn and on every page" how to avoid being taken in by scams and providing detailed information on how to report scams to the authorities.

She says the two key rules for avoiding online scams were to deal locally with people the renter could meet face-to-face and to never wire funds.

It's not just renters being fleeced in the current market, the FBI warns. In a twist to the scamming, landlords occasionally are contacted by potential "renters" who agree on a rental price. The scam renter then sends a check for the deposit on the rental property but shortly afterwards backs out of the rental agreement and asks for a refund.

Sometimes the landlord sends back a refund before realizing that the deposit check is counterfeit and hasn't been cleared by the bank.

Mr. Boone says that while some rogue operators have become increasingly creative in developing new methods of fleecing the public, many of the scams remained very simple. "But at the same time it's often that simplicity that catches people out," he says.